Semiconductor devices are commonly found in modern electronic products. Semiconductor devices vary in the number and density of electrical components. Discrete semiconductor devices generally contain one type of electrical component, e.g., light emitting diode (LED), small signal transistor, resistor, capacitor, inductor, and power metal oxide semiconductor field effect transistor (MOSFET). Integrated semiconductor devices typically contain hundreds to millions of electrical components. Examples of integrated semiconductor devices include microcontrollers, microprocessors, charged-coupled devices (CCDs), solar cells, and digital micro-mirror devices (DMDs).
Semiconductor devices perform a wide range of functions such as signal processing, high-speed calculations, transmitting and receiving electromagnetic signals, controlling electronic devices, transforming sunlight to electricity, and creating visual projections for television displays. Semiconductor devices are found in the fields of entertainment, communications, power conversion, networks, computers, and consumer products. Semiconductor devices are also found in military applications, aviation, automotive, industrial controllers, and office equipment.
Semiconductor devices exploit the electrical properties of semiconductor materials. The structure of semiconductor material allows its electrical conductivity to be manipulated by the application of an electric field or base current or through the process of doping. Doping introduces impurities into the semiconductor material to manipulate and control the conductivity of the semiconductor device.
A semiconductor device contains active and passive electrical structures. Active structures, including bipolar and field effect transistors, control the flow of electrical current. By varying levels of doping and application of an electric field or base current, the transistor either promotes or restricts the flow of electrical current. Passive structures, including resistors, capacitors, and inductors, create a relationship between voltage and current necessary to perform a variety of electrical functions. The passive and active structures are electrically connected to form circuits, which enable the semiconductor device to perform high-speed operations and other useful functions.
Semiconductor devices are generally manufactured using two complex manufacturing processes, i.e., front-end manufacturing, and back-end manufacturing, each involving potentially hundreds of steps. Front-end manufacturing involves the formation of a plurality of die on the surface of a semiconductor wafer. Each semiconductor die is typically identical and contains circuits formed by electrically connecting active and passive components. Back-end manufacturing involves singulating individual semiconductor die from the finished wafer and packaging the die to provide structural support and environmental isolation. The term “semiconductor die” as used herein refers to both the singular and plural form of the words, and accordingly, can refer to both a single semiconductor device and multiple semiconductor devices.
One goal of semiconductor manufacturing is to produce smaller semiconductor devices. Smaller devices typically consume less power, have higher performance, and can be produced more efficiently. In addition, smaller semiconductor devices have a smaller footprint, which is desirable for smaller end products. A smaller semiconductor die size can be achieved by improvements in the front-end process resulting in semiconductor die with smaller, higher density active and passive components. Back-end processes may result in semiconductor device packages with a smaller footprint by improvements in electrical interconnection and packaging materials.
FIG. 1a shows a portion of a reconstituted semiconductor wafer 10 including semiconductor die 12. A contact pad 14 is formed over an active surface of semiconductor die 12 with electrical connection to circuits in the active surface. An insulating or passivation layer 16 is formed over semiconductor die 12. An encapsulant 18 is deposited around semiconductor die 12 as part of reconstituted wafer 10. In FIG. 1b, a dielectric layer 20 is formed over insulating layer 16 and encapsulant 18. An opening 22 is formed in dielectric layer 20 to expose contact pad 14. In FIG. 1c, a multi-layer redistribution layer (RDL) is formed over dielectric layer 20 and into opening 22 to contact pad 14. The RDL includes conductive layer 24 conformally applied to dielectric layer 20 and into opening 22 to contact pad 14, and conductive layer 26 conformally applied to conductive layer 24. In FIG. 1d, a dielectric layer 28 is formed over dielectric layer 20 and conductive layers 24 and 26.
As described in FIGS. 1a-1d, the RDL requires several processes, including spin coating to form the dielectric layers and plating to form the conductive layers in accordance with standard photoresist procedures. The formation of the dielectric layers and conductive layers is time consuming and requires access to expensive and complex semiconductor processing equipment, such as a plating tool. In addition, the formation of the dielectric layers and conductive layers is difficult to achieve over a large semiconductor die area or large portion of the reconstituted wafer.